Picture coding and decoding apparatuses and methods performing variable length coding and decoding on a slice header stream and arithmetic coding and decoding on a slice data stream

ABSTRACT

A frame coding unit generates individual picture signal information from a moving picture signal, and outputs a frame code value which is a numeric value to be obtained as a result of coding picture signal information of each frame. A variable length coding unit decomposes the frame code value into unit frame code values which are basic units of coding, converts the unit frame code values into frame code words using only a single code table, and constructs a frame stream by combining the converted frame code words. A multiplexing unit multiplexes a header stream which is constructed through a method equivalent to a conventional method and the frame stream, and constructs a picture coded signal.

This application is a Divisional of application Ser. No. 10/415,329,which is the National Stage of International Application No.PCT/JP02/08240

TECHNICAL FIELD

The present invention relates to a picture coding method and a picturedecoding method, and particularly to a coding technique, a decodingtechnique and apparatuses thereof concerning data compression intendedfor recording/transmitting picture signals in an efficient manner.

BACKGROUND ART

In the age of multimedia which integrally addresses audio, video andother contents, existing information media, i.e., newspaper, magazine,television, radio, telephone and other means through which informationis conveyed to people, have recently come to be included in the scope ofmultimedia. Generally, multimedia refers to something that isrepresented by associating not only characters, but also graphics,voices, and especially pictures and the like together, but in order toinclude the aforementioned existing information media in the scope ofmultimedia, it appears as a prerequisite to represent such informationin digital form.

However, when calculating the amount of information contained in each ofthe aforementioned information media as the amount of digitalinformation, while the amount of information per character is 1˜2 bytesin the case of characters, the amount of information to be required is64 Kbits or over per second in the case of voices (telephone quality),and 100 Mbits or over per second in the case of moving pictures (currenttelevision reception quality), and it is not realistic for theaforementioned information media to handle such an enormous amount ofinformation as it is in digital form. For example, although video phonesare already in the actual use by using Integrated Services DigitalNetwork (ISDN) which offers a transmission speed of 64 Kbps-1.5 Mbps, itis not practical to transmit videos of televisions and cameras directlythrough ISDN.

Against this backdrop, information compression techniques have becomerequired, and moving picture compression techniques compliant with H.261and H.263 standards recommended by ITU-T (InternationalTelecommunication Union-Telecommunication Standardization Sector) areemployed for video phones, for example. Moreover, according toinformation compression techniques compliant with the MPEG-1 standard,it is possible to store picture information in an ordinary music CD(compact disc) together with sound information.

Here, MPEG (Moving Picture Experts Group) is an international standardon digital compression of moving picture signals, and MPEG-1 is astandard for compressing television signal information approximatelyinto one hundredth so that moving picture signals can be transmitted ata rate of 1.5 Mbps. Furthermore, since transmission speed within thescope of the MPEG-1 standard is limited primarily to about 1.5 Mbps,MPEG-2, which was standardized with a view to satisfy requirements forfurther improved picture quality, allows data transmission equivalent inquality to television broadcasting through which moving picture signalsare transmitted at a rate of 2-15 Mbps.

Furthermore, MPEG-4 which provides a higher compression ratio has beenstandardized by the working group (ISO/IEC JTC1/SC29/WG11) which wasengaged in the standardization of MPEG-1 and MPEG-2. Not only is itpossible to perform a highly efficient coding at a low bit rate, MPEG-4employs a powerful technique for error resilience which lessens thedegradation of picture quality to be judged from a subjectivestandpoint, even when a transmission channel error occurs.

Meanwhile, in existing picture coding such as H.263 and MPEG-4, avariety of signal conversion/compression processing are performed for apicture signal so as to covert such picture signal into various kinds ofvalues, and then either fixed length coding or variable length coding isperformed in accordance with code tables which are appropriatelyselected according to the meaning of each converted value. Generally,when coding is performed, a compression ratio is increased by allocatinga code word of a short code length to a code occurring with a highfrequency, and by allocating a code word of a long code length to a codeoccurring with a low frequency. Since values converted through signalconversion/compression processing are different in their occurrencefrequency depending on the meanings such values indicate, a compressionratio of picture coding is increased by making an appropriate selectionof code tables which describe code words corresponding to such values.In conventional picture decoding performed in a pair with conventionalpicture coding, a proper decoding is performed by using the same codetables as used in picture coding.

FIG. 1 is a functional block diagram showing units relating to codingfunctionality of an existing picture coding apparatus 500. Asillustrated in FIG. 1, the picture coding apparatus 500 is comprised ofa header/frame coding unit 501, a syntax analyzing unit 502, a fixedlength/variable length coding unit 503, and a code table selecting unit504.

The header/frame coding unit 501 acquires a moving picture signal Vin,and generates header information which is information common to anentire picture and moving picture signal information of each frame onthe basis of such moving picture signal Vin.

More specifically, the header/frame coding unit 501 generates, as theheader information, a header parameter (inf_H, not illustrated in thediagram) which is information common to the header, a header code value(InfVal_H) which is the header parameter converted into a value, and aheader syntax structure signal (Stx_H) indicating the value meaning ofthe header code value, outputs such header syntax structure signal(Stx_H) to the syntax analyzing unit 502, and outputs the header codevalue (InfVal_H) to the fixed length/variable length coding unit 503.Moreover, the header/frame coding unit 501 generates, as picture signalinformation of each frame, a frame code value (InfVal_F) which is avalue to be obtained as a result of coding the picture signal of eachframe, and a frame syntax structure signal (Stx_F) indicating the valuemeaning of the frame code value, outputs such frame syntax structuresignal (Stx_F) to the syntax analyzing unit 502, and outputs the framecode value (InfVal_F) to the fixed length/variable length coding unit503. Note that in FIG. 1, the header code value (InfVal_H) and the framecode value (InfVal_F) are collectively described as “InfVal_X”, and theheader syntax structure signal (Stx_H) and the frame syntax structuresignal (Stx_F) are collectively described as “Stx_X”.

The syntax analyzing unit 502 generates a code table selection signal(Sel_H or Sel_F) on the basis of either the header syntax structuresignal (Stx_H) or the frame syntax structure signal (Stx_F), and outputsit to the code table selecting unit 504. In other words, the syntaxanalyzing unit 502 generates a code table selection signal (e.g.Sel_H1˜Sel_H3, or Sel_F1˜Sel_F3) for selecting an appropriate code tablefrom a plurality of code tables on the basis of a value indicated by aheader syntax structure signal or a frame syntax structure signal. Notethat in FIG. 1, the code table selection signals (Sel_H and Sel_F) aredescribed collectively as “Sel_X”.

The fixed length/variable length coding unit 503 constructs a picturecoded signal (Str) on the basis of the header code value (InfVal_H) andthe frame code value (InfVal_F). To be more specific, the header codevalue (InfVal_H) is decomposed into unit header code values (Val_H: e.g.Val_H1˜Val_H3) which are basic units of coding. Then, code tables areselected by the code table selecting unit 504 based on these unit headercode values so as to obtain header code words (Code_H), and a headerstream (Str_H) is constructed by combining the header code value(InfVal_H) and the header code words (Code_H) together. Furthermore, thefixed length/variable length coding unit 503 decomposes the frame codevalue (InfVal_F) into unit frame code values (Val_F: e.g. Val_F1˜Val_F3)which are basic units of coding, selects code tables in the code tableselecting unit 504 based on these unit frame code values so as to obtainframe code words (Code_F), and constructs a frame stream (Str_F) bycombining the frame code value (InfVal_F) and the frame code words(Code_F) together. Furthermore, the fixed length/variable length codingunit 503 multiplexes the header stream (Str_H) and the frame stream(Str_F) so as to construct a picture coded signal (Str). Note that inFIG. 1, the unit header code values (Val_H) and the unit frame codevalues (Val_F) are collectively described as “Val_X”, and the headercode words (Code_H) and the frame code words (Code_F) are collectivelydescribed as “Code_X”.

As described above, the code table selecting unit 504 selects codetables on the basis of the code table selection signal Sel_X and theunit header code values or the unit frame code values, generates headercode words or frame code words according to such selected code tables,and outputs them to the fixed length/variable length coding unit 503.

FIG. 2 is a diagram showing a stream structure of a conventional picturecoded signal. The picture coded signal Str is comprised of frame dataFrmData in which picture signal information of each frame making up thepicture is stored and a sequence header SeqHdr which is informationcommon to each frame. Pieces of information making up the sequenceheader SeqHdr are a synchronizing signal SeqSync intended forsynchronization between transmission and receiving, a picture size Sizeof each frame and a frame rate FrmRate. Meanwhile, the frame dataFrmData is made up of macroblock data MB specific to macroblocks makingup a frame, and a frame header FrmHdr which is data common to eachmacroblock. The frame header FrmHdr is made up of a synchronizing signalFrmSync intended for synchronization among frames and a frame numberFrmNo that indicates a time at which the frame is displayed. Moreover,macroblock data MB is made up of a coding flag Cod indicating whethersuch macroblock is coded or not, a macroblock coding mode Modeindicating a coding method to be used for each macroblock, and whencoding is performed added with motion compensation, motion informationMV indicating the amount of such motion, and pixel value data Coef whichis coded data of each pixel.

FIG. 3 is a functional block diagram showing units relating to decodingfunctionality of an existing picture decoding apparatus 600. In thisdiagram, the same numbers are assigned to configurations that offer thesame functions and the signals that have the same meanings as those inthe functional diagram for the existing picture coding apparatus 500illustrated in FIG. 1, and explanations thereof are omitted.

A fixed length/variable length decoding unit 601 splits the picturecoded signal Str into the header stream (Str_H) and the frame stream(Str_F). Furthermore, the fixed length/variable length decoding unit 601decomposes the header stream (Str_H) into header code words Code_H (e.g.Code_H1˜Code_H3) which are basic units of decoding so as to obtain, in acode table selecting unit 602, the unit header code values (Val_H)corresponding to the header code words (Code_H), and constructs theheader code value (InfVal_H) by combining them. Moreover, the fixedlength/variable length decoding unit 601, as in the case of the aboveheader stream (Str_H), decomposes the frame stream (Str_F) into framecode words Code_F (e.g. Code_F1˜Code_F3) which are basic units ofdecoding so as to obtain, in the code table selecting unit 602, the unitframe code values Val_F corresponding to the frame code words Code_F,and constructs the frame code value (InfVal_F) by combining them.

A header/frame decoding unit 603 decodes the header code value(InfVal_H) so as to decompress the header information, and outputs theheader parameter (inf_H, not illustrated in the diagram) which isinformation common to the header and the header syntax structure signal(Stx_H) indicating the characteristic of the following header codevalue. The header syntax structure signal (Stx_H) here is informationindicating the meaning of the next code word which is necessary fordecoding such next code word in the header. Furthermore, theheader/frame decoding unit 603, as in the case of the above header codevalue (InfVal_H), decompresses the frame code value InfVal_F of eachframe, and outputs the frame syntax structure signal Stx_F and a decodedmoving picture signal Vout.

A syntax analyzing unit 604 outputs a code table selection signal(Sel_H) for switching an output of the code table selecting unit 602according to the header syntax structure signal (Stx_H) in order todecode the next code word in the header. In other words, the syntaxanalyzing unit 604 generates the code table selection signal (Sel_H) forswitching to an appropriate code table of a plurality of code tablesaccording to a value indicated by the header syntax structure signal(Stx_H). Furthermore, the syntax analyzing unit 604, as in the case ofthe above header syntax structure signal (Stx_H), outputs a code tableselection signal (Sel_F) according to the frame syntax structure signal(Stx_F).

The frame syntax structure signal Stx_F here is information indicatingthe characteristic of the next code word which is necessary for decodingsuch next code word. The syntax analyzing unit 604 outputs the codetable selection signal Sel_F for switching an output of the code tableselecting unit according to the frame syntax structure signal Stx_F inorder to decode the next code word. In other words, the syntax analyzingunit 604 generates the code table selection signal Sel_F for switchingto an appropriate code table of a plurality of code tables according toa value indicated by the frame syntax structure signal Stx_F. Note thatFIG. 3 also uses “InfVal_X”, Stx_X”, “Sel_X”, “Val_X”, “Code_X” asgeneric names common to signals concerning the header information andpicture signal information of each frame, as in the case of FIG. 1described above.

Note that the above-described header streams Str_H illustrated in FIG. 1and FIG. 3 correspond to the sequence header SeqHdr or the combinationof the sequence header SeqHdr and the frame header FrmHdr, and the framestreams Str_F correspond respectively to the frame data FrmData ormacroblock data MB illustrated in the stream structure of theconventional picture coded signal in FIG. 2.

Meanwhile, such existing picture coding apparatus and existing picturedecoding apparatus described above require a plurality of code tables inorder to increase a compression ratio, and there occurs a problem that

(1) processing for switching code tables becomes complicated. While thisdoes not pose a particular problem when coding/decoding is performed bya high-performance/large capacity computer, it is difficult to realizethis in a mobile terminal and the like with a small memory/low-computingpower. In particular, since code tables are frequently switchedaccording to the syntax structure signal (Stx_X) in the code tableselecting units 504 and 602 of the existing picture coding apparatus andthe existing picture decoding apparatus, processing for switching codetables can be complicated.

Meanwhile, there are two types of variable length coding, which areHuffman coding in which coding is performed using a code table which isrelatively easy to decode, and arithmetic coding which involves complexcoding/decoding processing but which offers highly-efficientcompression. Arithmetic coding is a kind of variable length coding, anda probability used for coding/decoding in arithmetic coding correspondsto a code table. However, when Huffman coding and arithmetic codingco-reside in the same stream in a complicated manner, there is a problemthat it is difficult for the aforementioned mobile terminal and the liketo realize this since processing for switching between Huffman codingand arithmetic coding in the course of coding and decoding is highlycomplicated.

The present invention has been conceived in order to solve the aboveproblem, and it is an object of the present invention to provide picturecoding methods and picture decoding methods that allow mobile terminalsand the like with small memory/low-computing power to carry out datacompression equivalent to conventional data compression.

DISCLOSURE OF INVENTION

The present invention is a picture coding method for coding informationincluding picture signals of each frame, wherein the information to becoded includes information concerning a characteristic of the wholepicture signal and information concerning the picture signals of eachframe, the picture coding method comprising: a plural coding step forperforming coding by the use of a plurality of coding methods for theinformation concerning the characteristic of the whole picture signal; acommon coding step for performing coding by the use of a coding methodcommon to each frame for the information concerning the picture signalsof each frame; and a multiplexing coding step for performing codingafter multiplexing the coded information concerning the characteristicof the whole picture signal and the coded information concerning thepicture signals of each frame.

Moreover, the present invention is a picture decoding method fordecoding multiplexed information including picture signals of eachframe, wherein the information to be decoded includes informationconcerning a characteristic of the whole picture signal and informationconcerning the picture signals of each frame, the picture decodingmethod comprising: a demultiplexing decoding step for demultiplexing theinformation concerning the characteristic of the whole picture signaland the information concerning the picture signals of each frame fromthe multiplexed information; a plural decoding step for performingdecoding by the use of a plurality of decoding methods for thedemultiplexed information concerning the characteristic of the wholepicture signal; and a common decoding step for performing decoding bythe use of a decoding method common to each frame for the demultiplexedinformation concerning the picture signals of each frame.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a functional block diagram showing units relating to codingfunctionality of the existing picture coding apparatus 500.

FIG. 2 is a diagram showing a stream structure of a conventional picturecoded signal.

FIG. 3 is a functional block diagram showing units relating to decodingfunctionality of the existing picture decoding apparatus 600.

FIG. 4 is a functional block diagram showing units relating to codingfunctionality of a picture coding apparatus according to the firstembodiment.

FIG. 5 is a stream structure diagram showing a picture coded signalcoded in the functional block diagram of the picture coding apparatusillustrated in FIG. 4.

FIG. 6A is a data structure diagram showing general frame data.

FIG. 6B is a data structure diagram showing the above frame data havingthe slice structure.

FIG. 7A is an example code table used when variable length coding isperformed in the picture coding apparatus.

FIG. 7B is an example c ode table used when fixed length coding isperformed in the picture coding apparatus.

FIG. 8 is a functional block diagram showing units relating to decodingfunctionality of a picture decoding apparatus according to the firstembodiment.

FIG. 9 is a flowchart showing a flow of coding processing of the picturecoding apparatus according to the first embodiment.

FIG. 10 is a functional block diagram relating to coding functionalityof a picture coding apparatus according to the second embodiment.

FIG. 11 is a functional block diagram relating to decoding functionalityof a picture decoding apparatus according to the second embodiment.

FIG. 12 is a functional block diagram showing units relating to codingfunctionality of the picture coding apparatus that separates headerinformation and individual picture signal information and performscoding for each of such information.

FIG. 13 is a functional block diagram showing units relating to decodingfunctionality of a picture decoding apparatus paired with the picturecoding apparatus illustrated in FIG. 12.

FIG. 14 are diagrams showing tables that list the coding methods in thefirst embodiment and the second embodiment.

FIG. 15A is a diagram showing an example physical format of a flexibledisk which is a recording medium in the third embodiment.

FIG. 15B is a diagram showing an external view of the flexible diskviewed from the front, a schematic cross-sectional view thereof, and theflexible disk.

FIG. 15C is a diagram showing an example system structure for recordingand reproducing a program to the flexible disk.

FIG. 16 is a block diagram showing an overview of a content supplysystem for carrying out content distribution service according to thefourth embodiment.

FIG. 17 is an example external view of a mobile phone.

FIG. 18 is an example functional configuration diagram of the mobilephone.

FIG. 19 is an example system structure diagram of a digital broadcastingsystem.

BEST MODE FOR CARRYING OUT THE INVENTION

The following explains preferred embodiments according to the presentinvention with reference to FIG. 4˜FIG. 19.

First Embodiment

FIG. 4 is a functional block diagram showing units relating to codingfunctionality of a picture coding apparatus 10 according to the presentembodiment. In FIG. 4, the same numbers are assigned to signalsconcerning the same operations as those of the signals of the existingpicture coding apparatus 500 illustrated in FIG. 1, and explanationsthereof are omitted.

The picture coding apparatus 10 according to the present embodiment ischaracterized by that a plurality of coding methods are employed for theheader which is information common to the whole picture signal and thata single coding method is employed for information relating to a picturesignal of each frame.

Note that this specification provides explanations for frames, butfields substitute as frames in the case of an interlace picture signal.

Note that configurations for generating and coding header informationwhich is information common to the whole picture signal and operationsthereof are identical to those of the above-explained existing picturecoding apparatus 500 illustrated in FIG. 1.

As illustrated in FIG. 4, the picture coding apparatus 10 newly includesa frame coding unit 13 and a variable length coding unit 16, as comparedto the existing picture coding apparatus 500 described above. Note thata multiplexing unit 17 is embodied by taking out some of the functionsof the fixed length/variable length coding unit 503 of theaforementioned existing picture coding apparatus 500.

The frame coding unit 13, which is a unit that generates individualpicture signal information from a moving picture signal Vin, outputs tothe variable length coding unit 16 a frame code value InfVal_F which isa value to be obtained as a result of coding picture signal informationof each frame with reference to a header parameter Inf_H.

The variable length coding unit 16 decomposes the frame code valueInfVal_F into unit frame code values Val_F which are basic units ofcoding, converts such unit frame code values Val_F into frame code wordsCode_F using only a code table 16 a, and constructs a frame stream Str_Fby combing such converted frame code words. Accordingly, a single codingmethod to be commonly used for all frames is employed for informationrelating to a picture signal of each frame, without switching betweencoding methods according to syntaxes as in the conventional case.

The multiplexing unit 17 multiplexes the header stream Str_H and theframe stream Str_F, and constructs a picture coded signal Str.

FIG. 5 is a stream structure diagram showing the picture coded signalStr in the picture coding apparatus 10 for which coding has beenperformed in the functional block diagram illustrated in FIG. 4. Asillustrated in FIG. 5, such stream is made up of a sequence headerSeqHdr and a plurality of frame data FrmData. In this case, the sequenceheader SeqHdr is information common to the whole picture signal andframe data FrmData is a piece of data that is coded by the use of onlythe code table 16 a.

Note that the sequence header SeqHdr and the frame data FrmData do notnecessarily have to be transmitted consecutively within the same streamand therefore that each of them may be transmitted in a differentstream, as long as the sequence header SeqHdr can be recognized first atthe decoding apparatus side.

FIG. 6 is a data structure diagram showing frame data illustrated inFIG. 5.

FIG. 6A is a data structure diagram showing general frame data FrmData.In this case, an example case is shown where the frame header FrmHdr ofthe frame data FrmData is coded by the use of a plurality of codingmethods (code tables) as common information of the whole picture signal,while macroblock data MB are coded by the use of a single coding method(e.g. only the code table 16 a). In this case, since macroblock data MBwhich occupy most of the stream are coded by the use of a single codingmethod (e.g. only the code table 16 a) in coding/decoding, there is noneed for processing for switching coding methods (code tables) which isrequired in the conventional case, meaning that it is possible toachieve a simplified picture coding apparatus having functionalityequivalent to that of existing picture coding apparatuses.

Note that the frame header FrmHdr and the macroblock data MB do notnecessarily have to be transmitted consecutively within the same stream.Each of them may be transmitted in a discontinuous manner within thesame frame or may be transmitted in a different stream as long as theframe header FrmHdr can be recognized first at the decoding apparatusside. In the stream structure shown in FIG. 6A, the frame header

FrmHdr of the frame data FrmData is described as common information ofthe whole picture signal. Note, however, that when one frame isconstructed by further combining a plurality of macroblocks as seen inthe slice structure of MPEG-1 and MPEG-2 as well as the video packetstructure of MPEG-4, and when such common information (header) as asynchronizing signal is placed at the top of such combination ofmacroblocks, the header of the combination of the macroblocks may beconfigured as information common to the whole picture signal and picturedata other than the header may be coded by the use of the single codetable 16 a. Such frame made up of the combination of the macroblocks isreferred to as a slice (Slice).

FIG. 6B is the data structure of frame data having the slice structurementioned above. A slice header SliceHdr is set as information common tothe whole picture signal and coded by the use of a plurality of codetables, and macroblock data of each slice Slice are coded by the use ofthe single code table 16 a. Note that the slice header SliceHdr andmacroblock data MB do not necessarily have to be transmittedconsecutively within the same stream. Each of them may be transmitted ina discontinuous manner within the same frame or may be transmitted in adifferent stream, as long as the slice header SliceHdr can be recognizedfirst at the decoding apparatus side.

FIG. 7 shows examples of a code table used in the present embodiment.FIG. 7A is an example code table used when variable length coding isperformed in the picture coding apparatus 10. As illustrated in FIG. 7A,the code length of code words corresponding to data “0”˜“2” that occurwith a high frequency is shorter, and the code length of code wordscorresponding to “3”˜“6” that occur with a low frequency is longer.

Meanwhile, FIG. 7B is an example code table when fixed length coding isperformed in the picture coding apparatus 10. As FIG. 7B shows, the codelengths of code words corresponding to each data are equal, but the codelength of code words becomes longer with the increase in the maximumnumber of frames to be memorized.

FIG. 8 is a functional block diagram showing units relating to decodingfunctionality of a picture decoding apparatus 20 according to thepresent embodiment. The picture decoding apparatus 20 decodes thepicture coded signal Str coded by the picture coding apparatus 10, andoutputs a decoded moving picture signal Vout. In FIG. 8, the samenumbers are assigned to signals concerning the same operations as thoseof the signals in the existing picture decoding apparatus 600illustrated in FIG. 3, and explanations thereof are omitted.

Note that configurations for decoding the header information which isinformation common to the whole picture signal and operations thereofare identical to those of the existing picture decoding apparatus 600illustrated in FIG. 3.

A demultiplexing unit 21 acquires the picture coded signal Str, anddemultiplexes it into the header stream Str_H and the frame streamStr_F. A variable length decoding unit 23 converts the frame code wordsCode_F making up the frame stream Str_F into unit frame code valuesVal_F by the use of only the code table 16 a, and constructs the framecode value InfVal_F which is a value of the signal coded from the unitframe code values Val_F. A frame decoding unit 27 decodes the frame codevalue InfVal_F referring to the header parameter Inf_H which isinformation common to the whole picture signal, and outputs the decodedmoving picture signal Vout.

As described above, since it is possible to decode the information otherthan the header which is information common to the whole picture signalby the use of only the single code table 16 a, there is no need forprocessing for frequently switching decoding methods (code tables) whichare required in the existing case, meaning that it is possible toachieve a simplified picture decoding apparatus having functionalityequivalent to the conventional decoding apparatuses.

Note that the header information which is information common to thewhole picture signal corresponds to the sequence header SeqHdr in thestream structure of the picture coded signal illustrated in FIG. 5 andto the frame header FrmHdr of the frame data illustrated in FIG. 6A. Asin the case of the picture coding apparatus 10 described above,macroblock data MB may be decoded by the use of a single code table 23a. Furthermore, as in the case of the picture coding apparatus 10described above, when the stream structure of a picture coded signal isthe slice structure, the slice header SliceHdr may be set as informationcommon to the whole picture signal and the information other than theslice header may be decoded by the use of only the single code table 23a.

Next, an explanation is given for the operations of the picture codingapparatus 10 with the above configuration.

FIG. 9 is a flowchart showing the flow of coding processing of thepicture coding apparatus 10.

First, when the moving picture signal Vin is inputted to a headerinformation generating unit 11 (S61), a code table used for coding theheader code value InfVal_H is selected on the basis of the header syntaxstructure signal Stx_H (S63). The header information generating unit 11and a fixed length/variable length coding unit 15 generate headerinformation on the basis of the moving picture signal Vin through amethod equivalent to the conventional one, select and code the codetables according to the decomposed unit header code values (Val_H)(S64˜S66), and construct the header stream (S67).

Meanwhile, a frame coding unit 13, on the acquisition of the movingpicture signal Vin (S61), performs coding for the information other thanthe header information by the use of only the code table 16 a (S68), andconstructs the frame stream (S69).

A multiplexing unit 17 multiplexes the header stream and the framestream so as to construct a picture coded signal (S70).

As described above, according to the picture coding apparatus and thepicture decoding apparatus according to the present embodiment, sincemacroblock data occupying most of the coding processing and decodingprocessing are coded and decoded by the use of a single code table,there is no need for processing for frequently switching code tableswhich is required in the conventional case, meaning that it is possibleto achieve a simplified picture coding apparatus having functionalityequivalent to that of the conventional coding apparatus

Second Embodiment

FIG. 10 is a functional block diagram showing units relating to codingfunctionality of a picture coding apparatus 30 according to the presentembodiment. In FIG. 10, the same numbers are assigned to signalsconcerning the same configurations and operations thereof as those inthe functional block diagram of the picture coding apparatus 10illustrated in FIG. 4, and explanations thereof are omitted.

Descriptions are provided for the difference between the picture codingapparatus 30 in FIG. 10 and the picture coding apparatus 10 in FIG. 4.The unit in the picture coding apparatus 10 that generates headerinformation which is common information of the whole picture signal,performs coding after selecting appropriate code tables from a pluralityof code tables, while the other individual picture signal informationare coded by the use of a single code table. The picture codingapparatus 30, on the other hand, performs coding for header informationwhich is common information of the whole picture signal through a fixedlength coding method or an ordinary variable length coding (Huffmancoding) method in which code tables are used, and the other individualpicture signal information are coded only through arithmetic coding.

Arithmetic coding involves slightly complicated coding/decodingprocessing as compared with such ordinary variable length coding asHuffman coding in which code tables are used, but is known as a methodthrough which a compression rate is increased. Therefore, by performing,in the course of decoding, ordinary variable length coding for headerinformation which is particularly important and which is wide invariety, it is possible to make a quick judgment as to what kind ofdecoding should be performed for frame data. Since arithmetic coding isweak against transmission errors and the like, significant effects interms of improving error resilience can be achieved by performingordinary variable length coding for header information which is animportant piece of data.

Moreover, considering that processing for switching from arithmeticcoding to ordinary variable length coding is particularly complicated,requiring a redundant number of bits, it is not wise to make frequentswitches between arithmetic coding and ordinary variable length coding.

A syntax analyzing unit 12 outputs to a coding selecting unit 31 acoding selection signal SelEnc for switching an output of the codingselecting unit 31 according to a header syntax structure signal Stx_H.

The coding selecting unit 31 selects either a fixed length coding methodor a variable length coding method according to a coding selectionsignal SleEnc, and coding is performed either in a fixed length codingunit 32 or a variable length coding unit 33 in accordance with theselected coding method so as to construct a header stream Str_H, andoutputs it to the multiplexing unit 17.

An arithmetic coding unit 34 performs arithmetic coding for a code valueInfVal_F referring to a header parameter Inf_H, constructs a framestream Str_F for which arithmetic coding has been performed, an outputsit to the multiplexing unit 17.

The multiplexing unit 17 multiplexes the header stream Str_H and theframe stream Str_F so as to construct a picture coded signal Str.

As described above, by switching coding methods according to syntaxes inorder to perform coding for the header information which is commoninformation of the whole picture signal, and by coding individualpicture signal information only through arithmetic coding in the picturecoding apparatus 30 according to the present embodiment, it is possibleto achieve a picture coding apparatus that allows a simplifiedprocessing for switching coding methods without lowering codingefficiency.

FIG. 11 is a functional block diagram relating to decoding functionalityof a picture decoding apparatus 40 according to the present embodiment.Note that in FIG. 11, the same numbers are assigned to signalsconcerning the same functional configurations and the same operations asthose of the picture decoding apparatus illustrated in the functionalblock diagram of the first embodiment, and explanations thereof areomitted.

Descriptions are provided for the difference between the picturedecoding apparatus 40 in FIG. 11 and the picture decoding apparatus 20according to the first embodiment. The picture coding apparatus 20, whendecoding the header information which is common information of the wholepicture signal, selects appropriate code tables from a plurality of codetables so as to perform decoding. While the picture decoding apparatus20 decodes the other individual picture signal information by the use ofa single code table, the picture decoding apparatus 40, when decodingthe header information which is common information of the whole picturesignal, performs decoding as an inverse processing of a fixed lengthdecoding method or an ordinary variable length coding (Huffman coding)method utilizing code tables, while decodes the other individual picturesignal information only through arithmetic coding. Note that the picturedecoding apparatus 40 in FIG. 11 is an apparatus for decoding thepicture coded signal Str which has been coded by the picture codingapparatus 30 in FIG. 10.

A syntax analyzing unit 26 outputs a decoding selection signal SelDecfor switching an output of a decoding selecting unit 41 according to theheader syntax structure signal Stx_H. The decoding selecting unit 41selects either a fixed length decoding method or a variable lengthdecoding method according to the decoding selection signal SelDec, andoutputs to a header information decoding unit 25 the header code valueInfVal_H which has been decoded either by a fixed length decoding unit42 or a variable length decoding unit 43 depending on the selecteddecoding method.

An arithmetic decoding unit 44 performs arithmetic decoding for theframe stream Str_F referring to the header parameter Inf_H, andconstructs the frame code vale InfVal_F for which arithmetic decodinghas been performed. A frame decoding unit 27 decodes the frame codevalue InfVal_F referring to the header parameter Inf_H which isinformation common to the entire signal, and outputs a decoded movingpicture signal Vout.

As described above, by switching to an efficient coding method accordingto syntaxes so as to code the header information which is commoninformation of the whole picture signal and by coding individual picturesignal information only through arithmetic coding, it is possible toachieve a picture decoding apparatus which allows a simplified switchingprocessing without lowering coding efficiency.

Note that, other than through the picture coding apparatuses 10 and 30as well as the picture decoding apparatuses 20 and 40 described above,it is also possible to realize coding and decoding of each piece ofinformation using a plurality of code tables by demultiplexing theheader information and individual picture signal information.

FIG. 12 is a functional block diagram showing units relating to codingfunctionality of a picture coding apparatus 50 that separates the headerinformation and individual picture signal information so as to performcoding for each piece of information.

Meanwhile, FIG. 13 is a functional block diagram showing units relatingto decoding functionality of a picture decoding apparatus 60 paired withthe picture coding apparatus 50 illustrated in FIG. 12.

FIG. 14 shows tables that list coding methods and decoding methodsemployed in the first embodiment and the second embodiment. In FIG. 14A,as shown in Method 1 for example, when coding header information(described as “Header information” in the diagram) and picture signalinformation relating to a picture signal of each frame (described as“Frame information” in the diagram), possible methods are an existingcoding method utilizing a code table (to be referred to as “code tablecoding” hereinafter) and coding through an arithmetic coding method (tobe referred to as “arithmetic coding” hereinafter). Moreover, it is alsopossible to perform coding for header information and frame informationthrough arithmetic coding (Method 2) or code table coding (Method 3)respectively.

Furthermore, as illustrated in FIG. 14B, when using code table codingfor both header information and frame information, possible cases areones where a “single” code table is used and where a method utilizing “aplurality of” code tables are used. More specifically, a coding methodin which a single code table is used (Method 3-1) or a coding method inwhich a plurality of code tables are used (Method 3-3) for both headerinformation and frame information may be used. In addition, it is alsopossible to employ a coding method in which a plurality of code tablesare used for header information and a single code table is used forframe information (Method 3-2), or a coding method in which a signalcode table is used for header information and a plurality of code tablesare used for frame information (Method 3-4).

Note that it should be understood that a single code table or aplurality of code tables may be employed for header information. Here,concerning a plurality of code tables, since specific coding methods aredetermined for the header which is information common to the wholepicture signal and for information relating to a picture signal of eachframe, the number of code tables to be employed is limited in advance,which minimizes the number of times for switching code tables.

The coding methods and the decoding methods in the first embodiment andthe second embodiment are characterized by that they have a plurality ofcoding/decoding methods (code tables) for information relating to theentire picture as in the conventional case but a common coding/decodingmethod is used for individual information relating to a picture signalof each frame. Generally, concerning information relating to the entirepicture, since the occurrence frequency of code words making up suchinformation greatly differs from code to code, a compression ratio isconsiderably decreased unless a plurality of coding/decoding methods areprovided. As for individual information, on the other hand, since codewords do not differ much in their number of occurrences as compared withinformation relating to the entire picture, a compression ratio does notget lowered much even if a common coding/decoding method is used.Furthermore, given that most of the processing time for coding/decodingis consumed for the processing intended not for information relating tothe entire picture but for individual information, there is asignificant effect from the viewpoint of apparatus implementation, ifindividual information can be coded/decoded through, preferably, asingle coding method. When comparing the advantage of switching betweena plurality of coding methods including switching between fixed lengthcoding and variable length coding, that it is easier with fixed lengthcoding to detect a synchronizing signal intended for synchronizationthan with variable length coding and that the use of a plurality ofcoding methods is suited from the viewpoint of high compression, withthe advantage of using a single coding method which allowscoding/decoding to be easily realized through a single coding method,this is especially effective in fields of application where the latteradvantage is bigger.

Also, considering that arithmetic coding is a kind of variable lengthcoding and that arithmetic coding, while providing a highly efficientcoding, requires complicated processing when used after being switchedespecially from fixed length coding or general variable length coding(Huffman coding), it is preferable that arithmetic coding is used as asingle coding method for individual information and a method other thanarithmetic coding is used for information relating to the entirepicture.

Third Embodiment

It is possible to record a program that realizes the picture codingmethods and the picture decoding methods presented in the firstembodiment or the second embodiment on a computer-readable recodingmedium such as a flexible disk and to carry out the processing presentedin each of the above embodiments on such a computer system as a personalcomputer.

FIG. 15 is a diagram explaining the case where such a program isexecuted on a computer system by the use of a flexible disk 1201 storingthe picture coding methods and the picture decoding methods explained inthe first embodiment and the second embodiment.

FIG. 15A illustrates an example physical format of the flexible disk1201 which is a recording medium. FIG. 15B shows an external view of theflexible disk viewed from the front, a schematic cross-sectional viewand the flexible disk. The flexible disk 1201 is contained in a case1202, and there are a plurality of tracks from the rim to the innerradius concentrically on the surface of the disk, each track beingdivided into 16 sectors in the angular direction. Therefore, in theflexible disk 1201 storing the above program, the program that realizesthe picture coding methods and the picture decoding methods describedabove is recorded in an allocated area on the disk.

Meanwhile, FIG. 15C shows a structure required for recording andreproducing the program on the flexible disk 1201. When recording theprogram on the flexible disk 1201, the program that realizes the picturecoding methods or the picture decoding methods is written via a flexibledisk drive 1203 by the use of a computer system 1204. Furthermore, whenconstructing the picture coding methods inside the computer system 1204using the program in the flexible disk, the program is read out from theflexible disk 1201 via the flexible disk drive 1203 and is transferredto the computer system.

Note that although the present embodiment explains the case where aflexible disk is used as a recording medium, an optical disc may also beused. Also, a recording medium is not limited to the above example andtherefore anything that is capable of recording programs such as an ICcard, a ROM cassette and the like is also in the scope of application.

Fourth Embodiment

The following explains an example of the present invention to be appliedto a system utilizing the picture coding apparatuses and the picturedecoding apparatuses presented in the above preferred embodiments.

FIG. 16 is a block diagram showing the general view of a content supplysystem 100 for carrying out a content distribution service. This contentsupply system 100 is made up of a cellular network 104 for mobilephones, for example, and is connected to a computer 111, a PDA (PersonalDigital Assistants) 112, a camera 113, a mobile phone 114 and others viabase stations 107-110.

The camera 113, an example of which is a digital video camera and thelike, is capable of taking moving pictures. The mobile phone 115 is amobile phone in the PDC (Personal Digital Communications) system, theCDMA (Code Division Multiple Access) system, the W-CDMA (Wideband-CodeDivision Multiple Access) system, or the GSM (Global System for MobileCommunications) system or the like, or a PHS (personal HandyphoneCommunications) terminal device and the like.

Moreover, a streaming server 103, which is connected to the cellularnetwork 104 via a dedicated network for server connection 105 or theInternet 101 and the like, allows the live distribution and the like ofcoded data of a picture taken by the camera 113. In this case, codingprocessing for the picture may be performed either by the camera 113 orby a server 113 a connected to such camera. It is also possible thatpicture data of a picture taken by a camera 116 is transmitted to thestreaming server 103 via the computer 111. Here, the camera 116 is adigital camera, for example, and is capable of taking still pictures. Inthis case, coding of the picture data may be performed either by thecamera or by the computer 111. Moreover, the above coding processing isperformed by an LSI 117 embedded in the camera 116 or the computer 111.Furthermore, picture data taken by a camera-equipped mobile phone 115may also be transmitted. The picture data in this case is data coded byan LSI incorporated in the mobile phone.

Note that software for picture coding/decoding may be stored in arecording medium (e.g. storage medium including a CD-ROM, a flexibledisk, a hard disk or the like) which can be read by the computer 111 orothers.

FIG. 17 is an example external view of the mobile phone 114. As FIG. 17shows, the mobile phone 114 has an antenna 201, a camera unit 203 thatemploys the CCD system or the like capable of taking moving pictures andstill pictures, a displaying unit 202 such as a liquid crystal displayand the like to display videos and the like taken by the camera unit 203and videos and the like received via the antenna 201, a main body 204having a group of operation keys, a sound outputting unit 208 having aspeaker and the like for outputting sound, a sound inputting unit 205having a microphone and the like for inputting sound, a recording medium207 for storing data of taken/received moving pictures and stillpictures or received mail data and the like, a slot 206 for attachingthe recording medium 207. The recording medium 207, an example of whichis an SD card, stores inside a plastic case a flash memory which is akind of volatile memory EEPROM (Electrically Erasable and ProgrammableRead Only Memory).

In the content supply system 100, while the contents (e.g. shot videosof live music, etc.) taken by the user using the camera 113, the camera116 and the like is coded and transmitted to the streaming server 103,the streaming server 103 carries out stream distribution for the abovecontent data to a client requesting such content data. Such client canbe the computer 111, the PDA 112, the camera 113, the mobile phone 114and others capable of decoding the coded data.

The content supply system 100 with the above structure makes it ispossible for a client to receive and reproduce coded data as well asrealizing private broadcasting by allowing a client to receive codeddata in real time, decode and reproduce it.

Furthermore, an explanation is given for the mobile phone 114 withreference to FIG. 18. The mobile phone 114 is configured in a manner inwhich a main controlling unit 311 that has a general control of thedisplaying unit 202 and each unit of the main body 204, a power supplycircuit unit 310, an operation input controlling unit 304, a picturecoding unit 312, a camera controlling unit 303, an LCD (Liquid CrystalDisplay) controlling unit 302, a picture decoding unit 309, ademultiplexing unit 308, a recording and reproducing unit 307, a modemcircuit unit 306, and a sound processing unit 305 are interconnected viaa bus 313. When the power key is set to ON by a user operation, thepower supply circuit unit 310 activates the camera-equipped mobile phone114 to make it ready for operations by supplying power for each unitfrom the battery pack. Under the control of the main controlling unit311 having a CPU, a ROM, a RAM and others, the mobile phone 114 convertsa sound signal collected by the sound inputting unit 205 when in theconversation mode to digital sound data in the sound processing unit305, performs spread spectrum processing for it in the modem circuitunit 306, and after performing digital-analog conversion processing andfrequency transform processing in the transmit/receive circuit unit 301,transmits this data via the antenna 201. Furthermore, the mobile phone114 amplifies the signal received by the antenna 201 while in theconversation mode so as to perform frequency transform processing andanalog-digital conversion processing, performs inverse spread spectrumprocessing in the modem circuit unit 306, and after converting this intoan analogue sound signal in the sound processing unit 305, outputs itvia the sound outputting unit 208. Furthermore, when sending e-mailwhile in the data communication mode, text data inputted via theoperation input controlling unit 304 on the main body 204 is exported tothe main controlling unit 311. The main controlling unit 311 performsspread spectrum processing for the text data in the modem circuit unit306, and after performing digital-analog conversion processing andfrequency transform processing in the transmit/receive circuit unit 301,transmits it to the base station 110 via the antenna 201.

When picture data is transmitted while in the data communication mode,the main controlling unit 311 provides picture data taken by the cameraunit 203 to the picture coding unit 312 via the camera controlling unit303. When picture data is not to be transmitted, it is possible todirectly display the picture data taken by the camera unit 203 on thedisplay unit 202 via the camera controlling unit 303 and the LCDcontrolling unit 302.

By performing compression coding for the picture data provided from thecamera unit 203 using the coding methods presented in the aboveembodiments, the picture coding unit 312 converts the picture data tocoded picture data, and transmits it to the demultiplexing unit 308.When this is done, the mobile phone 114 transmits sound collected by thesound inputting unit 205 while the picture is being taken by the cameraunit 203, to the demultiplexing unit 308 as digital sound data via thesound processing unit 305.

The demultiplexing unit 308 multiplexes the coded picture data providedfrom the picture coding unit 312 and the sound data provided from thesound processing unit 305 through a specified method and performs spreadspectrum processing for the resulting multiplexed data in the modemcircuit unit 306, and after performing digital-analog conversionprocessing and frequency transform processing in the transmit/receivecircuit unit 301, transmits it via the antenna 201.

When receiving moving picture file data linked on a Web page and thelike while in the data communication mode, inverse spread spectrumprocessing is performed by the modem circuit unit 306 for a signalreceived from the base station 110 via the antenna 201, and theresulting multiplexed data is delivered to the demultiplexing unit 308.

In order to decode the multiplexed data received via the antenna 201,the demultiplexing unit 308 divides such multiplexed data into the codedpicture data and the sound data by demultiplexing it, and provides thecoded picture data to the picture decoding unit 309 while providing thesound data to the sound processing unit 305 via the bus 313 at the sametime.

Next, the picture decoding unit 309 generates moving picture data forplayback by decoding the coded picture data through decoding methodsused in a pair with the coding methods presented in the aboveembodiments, and provides it to the display unit 202 via the LCDcontrolling unit 302, as a result of which the picture data included inthe moving picture file linked to a Web page, for example, can bedisplayed. When this is done, the sound processing unit 305 converts thesound data to an analog sound signal at the same time and then providesit to the sound outputting unit 208, as a result of which the sound dataincluded in the moving picture file linked to a Web page, for example,can be reproduced.

Note that the aforementioned system is not an exclusive example andtherefore that at least either the coding methods or the decodingmethods of the above embodiments can be incorporated into a digitalbroadcasting system as shown in FIG. 19, against the backdrop thatsatellite/terrestrial digital broadcasting has been a recent topic ofconversation. To be more specific, at a broadcasting station 409, acoded bit stream of video information is transmitted to a satellite 410for communications, broadcasting or the like by radio waves. Thesatellite 410 that has received this receives broadcast radio waves,receives such radio waves by an antenna 406 of a house equipped withsatellite broadcasting reception facilities, and the coded bit streamare then decoded by such an apparatus as a television receivingequipment 401 or a set top box 407 so as to reproduce the decoded data.Furthermore, it is possible to implement the decoding methods presentedin the above embodiments in a reproducing apparatus 403 that reads anddecodes a coded bit stream recorded in a storage medium 402 which is arecording medium. In this case, a reproduced video signal is displayedon a monitor 404. Another possible configuration is that a decodingapparatus is implemented inside the set top box 407 which is connectedto a cable 405 for cable televisions or to the antenna 406 forsatellite/terrestrial broadcasting and the reproduced video signal isdisplayed on a television monitor 408. In such a case, a decodingapparatus may be incorporated not into the set top box but into thetelevision. Moreover, it is also possible for a car 412 having anantenna 411 to receive a signal from the satellite 410 or from the basestation 107 and the like, and to display a moving picture on such adisplaying device of the car 412 as a car navigation system 413 and thelike.

A possible configuration of the car navigation system 413 is theconfiguration illustrated in FIG. 18 from which the camera unit 203 andthe camera controlling unit 303, for example, are excluded. The same isalso applicable to the computer 111, the television receiving equipment401 and others. Concerning terminals such as the mobile phone 114, atransmitting/receiving terminal having both a coder and a decoder, aswell as a transmitting terminal only with a coder and a receivingterminal only with a decoder are possible as forms of implementation.

As stated above, by implementing the coding methods and the decodingmethods described above, it is possible to embody the present inventionas any one of the apparatuses and the system presented in theaforementioned embodiments.

INDUSTRIAL APPLICABILITY

As described above, it is possible for the picture coding methods andthe picture decoding methods according to the present invention torealize coding processing and decoding processing through which datacompression equivalent to conventional one and to reduce processing loadto be generated at the time of selecting code tables, and others.Therefore, the picture coding methods and the picture decoding methodsaccording to the present invention are suited as picture coding methodsand picture decoding methods for mobile phones, mobile informationterminals and others that do not have sufficient processing capabilityand storage capacity.

1. A coding device that codes a moving picture on a block basis, saidcoding device comprising: a header information generating unitconfigured to receive a moving picture signal and to generate, based onthe moving picture signal, a header parameter and a header code valuesignal corresponding to the header parameter according to a syntaxstructure signal, the header parameter and the header code value signalbeing common to a plurality of blocks of moving picture signals; aheader information coding unit configured to perform non-arithmeticcoding on the header code value signal selectively with either a fixedlength code or a variable length code according to the syntax structuresignal, so as to generate a header stream; a frame coding unitconfigured to code, on the block basis, the moving picture signal withreference to the header parameter so as to generate a frame code valuesignal; an arithmetic coding unit configured to perform only arithmeticcoding on the frame code value signal so as to construct a frame stream;and a multiplexer configured to multiplex the header stream and theframe stream so as to construct a picture coded signal, wherein theheader information coding unit includes: a fixed length coding unit forfixed length coding a plurality of header code value signals accordingto at least one of a plurality of fixed length coding methods; avariable length coding unit for variable length coding the plurality ofheader code value signals according to at least one of a plurality ofvariable length coding methods; and a coding selecting unit configuredto select one of the fixed length coding unit or the variable lengthcoding unit according to the syntax structure signal, and wherein theheader information coding unit is configured to code the header codevalue signal corresponding to the fixed length code, using one of theplurality of fixed length coding methods according to the syntaxstructure signal, when the fixed length coding unit is selected by thecoding selecting unit, and the header information coding unit isconfigured to code the header code value signal corresponding to thevariable length code, using one of the plurality of variable lengthcoding methods according to the syntax structure signal, when thevariable length coding unit is selected by the coding selecting unit.